We propose to study the interaction of circulating catecholamines and the renal baroreceptors in the regulation of renin release in the conscious, trained dog. We have demonstrated that dopamine infused into the renal artery stimulates release of renin. We shall now attempt to determine the physiological role of dopamine receptors in the release of renin. In addition we shall use electron probe microanalysis to study the renal transport sodium-potassium-ATPase in renovascular hypertension induced in normal rats and rats with hereditary diabetes insipidus (Brattleboro strain).